My bike died and then came to life again

enargins

1 mW
Joined
Aug 15, 2018
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12
So I was out for a short ride with my Ancheer 250W bike. Battery was about half charged when I started. After going about 2 miles, I went up a slight hill, and then, at the top of the hill, the bike died, and I couldn't restart it. I rode it without power the rest of the way.

When I got home I charged the battery. But even after the battery was fully charged, it wouldn't start. The battery was switched on. Also the headlight, which uses the battery's power, was switched on, but it wasn't lit. So neither the bike nor the headlight was getting any power.

I then turned the battery off and then on again, and then everything worked again.

Anyone have any idea what was going on? I don't believe the battery was fully drained. Like I said, it was half full when I started, and I only went a couple of miles. Also, the battery only took like an hour to be fully charged again. So I don't think it was completely drained. But there was no power to the control pad on the handlebar, nor to the headlight.

Any ideas are appreciated.

Thanks.
 
Sounds like the BMS on the battery tripped. Most likely you were drawing more current than the BMS or Battery could handle when you went uphill, and it or the Battery overheated.

The BMS only resets after you unplug it from the bike.
 
Thanks. That sounds likely. A few questions.

1) What is a BMS? What does BMS stand for?

2) I didn't unplug the BMS. I just turned off the battery with the switch that's on the battery, and then turned the battery back on again. Would that reset the BMS?

3) My motor has three levels. I was going up the slight hill at level 1, because I wanted to use my legs as much as possible, and only use the electric motor a little bit. If I had had the motor on level 2 or 3, might that have prevented this situation, since more current would have been flowing to the motor?

Thanks!
 
The BMS is The Battery management System that monitors each individual cell inside the Battery Pack.
Your BMS happens to have a switch, so you don't need to unplug it to reset it.

Going by what you said it, the Battery might not have been stressed at all. Since the Motor should not draw as much as it needs in the 2nd or 3rd assist level.

It'd be nice if you could do a few tests. Like going up that hill again with the 2nd or 3rd assist level. And checking the temperature of the Battery after it shuts down on you again.

The only two other things that I can think of (If it's not overcurrent) are, the Battery overheating (like a black case getting really hot from the sun, and getting hotter with additional power draw) which caused the BMS to shut down.

Or a wire with an intermittent short, that tripped the BMS to protect the Battery.

Check any loose wires that could rub against the Frame of the Bike or anything like that.
 
Thanks for the explanation. I don't think it was overheating due to temp. The ride was in early morning, before the sun came up, and it was in the low 80's. So I think the battery itself was cool from external temps.

I'll try to do the test and will look for any loose wires.

One thing I'll note is that if I go up a steeper hill, the motor makes a loud, sort of screeching noise. Could be I'm stressing it too much. It's only 250W, and the bike has a max load of 250 lbs, but I weigh 330. But I've never had it turn off before. Possibly because the battery was only half charged?

I did note that, even when the battery is fully charged (5 lights on the control pad), and I go up a hill, the charge lights go down to 3 lights while going up the hill, then go back to 5 lights afterwards. Not sure why that is. This time, the battery was at 3 lights to begin with, and then I went up the hill. So maybe that over-stressed the battery?

Just throwing out some ideas here.

Thanks!
 
If it's a brushless motor then it might be one of the sensors has simply died,
or one of the wires coming out of the Axle has been cut from the vibration.

This causes the motor to vibrate/rumble under load and also consume much more than it's supposed to. :!:
another sign of a broken sensor, is that the motor won't start in some positions from a stand still.

The reason why the lights on the throttle dimm is because the LEDs act like a voltmeter,
and when you put a load on a battery (or even your 110V socket) it causes the voltage to drop temporarily until the load is removed, and since it's also an indicator of battery capacity you see the LEDs go from yellow to green again and vice versa.
 
eee291 said:
If it's a brushless motor then it might be one of the sensors has simply died,
or one of the wires coming out of the Axle has been cut from the vibration.

Specs say it's a 250W high speed brushless gear motor. So, yeah, I guess it's brushless

The reason why the lights on the throttle dimm is because the LEDs act like a voltmeter,
and when you put a load on a battery (or even your 110V socket) it causes the voltage to drop temporarily until the load is removed, and since it's also an indicator of battery capacity you see the LEDs go from yellow to green again and vice versa.

That's good to know. Thanks!
 
*** UPDATE ***

So, I just took the bike out again (sun is down; 85F outside). Battery was fully charged. Let friend ride it for about 10 minutes. Then rode it myself. After a couple of minutes I went up a hill. Put power level on 2 (out of 3) and then on 3. Battery/voltmeter went down to 3 lights instead of 5 (as it always does when I go up a hill).

At top of the hill, bike died again. Turned battery off and on and restarted bike. Was fine the rest of the way. Voltmeter went back to 4 lights, then 5 lights the rest of the way. So, was plenty of charge in the battery.

Now, I'll just say that I've taken this bike up many hills before on level 2 and 3, usually with a 60 lb trailer attached and a 20 lb dog. So this was less weight than that. And I've ridden this bike at least a few dozen times since I've had it. Never had this problem going up hills before. This is now 2 times in a row. And right when I got started.

I will say that, because of the hot days, I let the bike sit with a half-charged battery for a couple of months before I rode it again for the first time yesterday. I don't know if letting it sit that long without being fully charged damaged something with the battery. But something has changed.

Like I said, I've ridden this many times with much more weight up hills and never had this problem before. Now it's twice in a row. So what happened? Any ideas?

Thanks!
 
It's a jesus bike.

It sounds like going up the hill put too much load on your battery and it sagged very heavily and tripped the low voltage cut off in the BMS.

Once the load was removed from the pack the voltage rose again and so started working again.

There is a chance that the pack has lost a cell or two.

What is the config of the pack and which cells are used?
 
Yes, I'm sure that's what happened. The question is: why is this happening now, when I've ridden this bike dozens of times up hills with heavier loads without any problem? Like you said, maybe the pack lost a cell or two (perhaps from sitting half-charged for several months?).

As for the config, I'm a total noob, so not sure what that is. I went to the bike's web page, though (https://www.amazon.com/gp/product/B...beb-4819111bef9a&pf_rd_r=3ASZ60P7PSYJW0145QJN) and found this: 36V, 8AH Ion lithium battery. Is that what you were looking for?
 
Not a lot of info given about the battery they supply. No info about how many cells, what cells are used etc.

It will either be a 10S4P of 2000mAh cells or a 10S3P of 2600mAh cells. Given the price of the bike and the fact that there are no details given (if it was made with quality cells it would be marketed as such), it's likely made from generic chinese cells.

If that's the case, there is a good chance that one or more cells have given up. If one cell is dead, given that its a tiny battery, it will significantly impact on the performance of the pack.

It might be time to get the pack rebuilt locally with quality cells, or buy a whole new pack.

If you are so inclined, you could open up the battery and inspect it for any issues. If a cell is gone it may have vented and you will probably see the signs of this, such as electrolyte stains on the top of a cell.
 
They sell those batteries new on eBay for $190 (with 10aH instead of the 8aH that mine has). So I think I would do that, if I was sure it was the battery.

Read a post somewhere about a gal who had similar problem as mine, and she replaced the battery, but it didn't solve the problem.

So, while battery seems likely, not 100% sure about it.

Also, am being told that 8aH is way too small for my weight and should have much more, which makes sense. So, am considering options there.
 
Hi. Curious please? Can't see where you mentioned numbers of cycles used on the battery... ie how old is the bike/battery... and "used much"? Like, any way any contact connections could be "dirty"/rusted/etc such that they easily overheat, after, for example going up any hills? [smile] You DO have a multmeter to "test stuff", correct? :wink:
 
Bike is fairly new, hardly used. No way the contacts are rusted. Thanks for the thought, though.
 
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